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Expansion Vessels

Heating and Plumbing World are delighted to give their customers an extensive selection of expansion tank vessels from industry leading brands. Zilmet, Reflex, Altecnic and Flamco are all manufacturers with stellar reputations earned due to unfailing quality and reliability of their products. You...
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Heating and Plumbing World are delighted to give their customers an extensive selection of expansion tank vessels from industry leading brands. Zilmet, Reflex, Altecnic and Flamco are all manufacturers with stellar reputations earned due to unfailing quality and reliability of their products. You’ll find heating expansion vessels and potable expansion vessels available for a fraction of the price you’d pay anywhere else. If you need assistance with expansion tank sizing, don’t hesitate to get in touch.

What is an expansion vessel?

Expansion vessels accommodate fluctuations in the water pressure inside a plumbing system. Older vessels simply allow water to rise into an overflow tank and return by gravity, however, sealed systems are more hygienic and energy-efficient. Modern vessels are divided by a flexible internal diaphragm that keeps the air and water separate.

What pressure should my expansion vessel be?

In typical domestic systems, the pressure inside expansion vessels is factory pre-set to about 12psi (0.82 bar). However, it varies between makes and can be adjusted for taller buildings, higher system pressures or altitude. Some are as high as 20psi (1.38 bar). If you can’t find the specifications on the vessel, contact the manufacturer.

Whether you need 50 litre expansion vessels or 0.5 litre expansion tanks, we’ll help you find the right product. Similarly, if you are uncertain about the expansion vessel installation process, you needn’t wait to contact us to get the advice you need. Any and all expansion tank problems can be resolved quickly and easily with the guidance of our expert team. Call or email Heating and Plumbing World today to get the help you need to find a reliable solution for your heating system that works long-term.

How to size an expansion vessel?

When the system’s water volume is unknown, you can estimate the expansion volume from the boiler power. Most 25kW boilers can use a 24ltr vessel, 60kW boilers need a 50ltr vessel, and a 120kW boiler needs at least a 100ltr vessel. However, there are other factors so it is always wise to consult an engineer.

How does an expansion vessel work?

Water expands as it heats, so modern sealed expansion vessels contain a diaphragm that expands and contracts, accommodating changes in water volume and pressure. Water from the vessel returns to the system as it contracts - maintaining a constant safe pressure at all temperatures. Being sealed, the water is also protected from contamination.

What size expansion vessel for heating system?

The rule of thumb for systems with a pressure of up to 1.5 bar is that you need 1 litre capacity for each kW of output from the boiler. You should always round up, so a boiler with 160 kW output should have a 200 litre expansion vessel.

How much is a boiler expansion vessel?

Small expansion vessels, suitable for use within home central heating systems can be found for less than £50. For larger central heating systems used in commercial properties, the cost will rise from a few hundred pounds to upwards of £1000 for the largest expansion vessels.


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